3 files changed, 121 insertions, 1 deletions
diff --git a/packages/integrations/vercel/src/serverless/entrypoint.ts b/packages/integrations/vercel/src/serverless/entrypoint.ts
index e41d0a438..daa811015 100644
--- a/packages/integrations/vercel/src/serverless/entrypoint.ts
+++ b/packages/integrations/vercel/src/serverless/entrypoint.ts
@@ -3,12 +3,21 @@ import type { SSRManifest } from 'astro';
 import { App } from 'astro/app';
 import type { IncomingMessage, ServerResponse } from 'node:http';
 
-import { getRequest, setResponse } from './request-transform.js';
+import * as requestTransformLegacy from './request-transform/legacy.js';
+import * as requestTransformNode18 from './request-transform/node18.js';
 
 polyfill(globalThis, {
 	exclude: 'window document',
 });
 
+// Node 18+ has a new API for request/response, while older versions use node-fetch
+// When we drop support for Node 14, we can remove the legacy code by switching to undici
+
+const nodeVersion = parseInt(process.version.split('.')[0].slice(1)); // 'v14.17.0' -> 14
+
+const { getRequest, setResponse } =
+	nodeVersion >= 18 ? requestTransformNode18 : requestTransformLegacy;
+
 export const createExports = (manifest: SSRManifest) => {
 	const app = new App(manifest);
 
diff --git a/packages/integrations/vercel/src/serverless/request-transform/legacy.ts b/packages/integrations/vercel/src/serverless/request-transform/legacy.ts
new file mode 100644
index 000000000..7212431c7
--- /dev/null
+++ b/packages/integrations/vercel/src/serverless/request-transform/legacy.ts
@@ -0,0 +1,111 @@
+import type { App } from 'astro/app';
+import type { IncomingMessage, ServerResponse } from 'node:http';
+import { Readable } from 'node:stream';
+
+const clientAddressSymbol = Symbol.for('astro.clientAddress');
+
+/*
+  Credits to the SvelteKit team
+	https://github.com/sveltejs/kit/blob/69913e9fda054fa6a62a80e2bb4ee7dca1005796/packages/kit/src/node.js
+*/
+
+function get_raw_body(req: IncomingMessage) {
+	return new Promise<Uint8Array | null>((fulfil, reject) => {
+		const h = req.headers;
+
+		if (!h['content-type']) {
+			return fulfil(null);
+		}
+
+		req.on('error', reject);
+
+		const length = Number(h['content-length']);
+
+		// https://github.com/jshttp/type-is/blob/c1f4388c71c8a01f79934e68f630ca4a15fffcd6/index.js#L81-L95
+		if (isNaN(length) && h['transfer-encoding'] == null) {
+			return fulfil(null);
+		}
+
+		let data = new Uint8Array(length || 0);
+
+		if (length > 0) {
+			let offset = 0;
+			req.on('data', (chunk) => {
+				const new_len = offset + Buffer.byteLength(chunk);
+
+				if (new_len > length) {
+					return reject({
+						status: 413,
+						reason: 'Exceeded "Content-Length" limit',
+					});
+				}
+
+				data.set(chunk, offset);
+				offset = new_len;
+			});
+		} else {
+			req.on('data', (chunk) => {
+				const new_data = new Uint8Array(data.length + chunk.length);
+				new_data.set(data, 0);
+				new_data.set(chunk, data.length);
+				data = new_data;
+			});
+		}
+
+		req.on('end', () => {
+			fulfil(data);
+		});
+	});
+}
+
+export async function getRequest(base: string, req: IncomingMessage): Promise<Request> {
+	let headers = req.headers as Record<string, string>;
+	if (req.httpVersionMajor === 2) {
+		// we need to strip out the HTTP/2 pseudo-headers because node-fetch's
+		// Request implementation doesn't like them
+		headers = Object.assign({}, headers);
+		delete headers[':method'];
+		delete headers[':path'];
+		delete headers[':authority'];
+		delete headers[':scheme'];
+	}
+	const request = new Request(base + req.url, {
+		method: req.method,
+		headers,
+		body: await get_raw_body(req), // TODO stream rather than buffer
+	});
+	Reflect.set(request, clientAddressSymbol, headers['x-forwarded-for']);
+	return request;
+}
+
+export async function setResponse(
+	app: App,
+	res: ServerResponse,
+	response: Response
+): Promise<void> {
+	const headers = Object.fromEntries(response.headers);
+
+	if (response.headers.has('set-cookie')) {
+		// @ts-expect-error (headers.raw() is non-standard)
+		headers['set-cookie'] = response.headers.raw()['set-cookie'];
+	}
+
+	if (app.setCookieHeaders) {
+		const setCookieHeaders: Array<string> = Array.from(app.setCookieHeaders(response));
+		if (setCookieHeaders.length) {
+			res.setHeader('Set-Cookie', setCookieHeaders);
+		}
+	}
+
+	res.writeHead(response.status, headers);
+
+	if (response.body instanceof Readable) {
+		response.body.pipe(res);
+	} else {
+		if (response.body) {
+			res.write(await response.arrayBuffer());
+		}
+
+		res.end();
+	}
+}
diff --git a/packages/integrations/vercel/src/serverless/request-transform.ts b/packages/integrations/vercel/src/serverless/request-transform/node18.ts
index a42bac1f5..a42bac1f5 100644
--- a/packages/integrations/vercel/src/serverless/request-transform.ts
+++ b/packages/integrations/vercel/src/serverless/request-transform/node18.ts